Embodiments of the invention relate to a polycrystalline diamond (PCD) structure, elements comprising same, method for making same and tools comprising same, particularly but not exclusively for use in rock degradation or drilling, or for boring into the earth.
PCD material comprises a mass of substantially inter-grown diamond grains and interstices between the diamond grains. PCD may be made by subjecting an aggregated mass of diamond grains to an ultra-high pressure and temperature in the presence of a sintering aid such as cobalt, which may promote the inter-growth of diamond grains. The sintering aid may also be referred to as a catalyst material for diamond. Interstices within the PCD material may be wholly or partially filled with residual catalyst material. PCD may be integrally formed on and bonded to a cobalt-cemented tungsten carbide substrate, which may provide a source of cobalt catalyst material for sintering the PCD. As used herein, the term “integrally formed” regions or parts are produced contiguous with each other and are not separated by a different kind of material. Tool inserts comprising PCD material are widely used in drill bits used for boring into the earth in the oil and gas drilling industry. Although PCD material is extremely abrasion resistant, there is a need for PCD tool inserts that have enhanced fracture resistance.
PCT patent application publication number WO/2004/111284 discloses a composite material comprising a plurality of cores of PCD dispersed in a matrix comprising a PCD material of a grade different to that of the cores, and a suitable binder.